1. Field of the Invention
The present invention relates to an insert molding die for molding a hollow component and an insert molding method thereof.
2. Description of the Related Art
Conventionally, when producing such a hollow component by insert molding using molten resin, it is first performed to open a molding die having an upper die and a lower die and successively, a primary molded piece is accommodated in the lower die. Here noted, this primary molded piece is an element to form a hollow part in the hollow component. After positioning the primary molded piece in the lower die, the upper and lower dies are closed to complete the molding die. In this state, it is started to inject molten resin into a cavity defined in the molding die. In this way, the cavity is filled up with molten resin (Japanese Patent Application Laid-open No. 10-6348).
In the above-mentioned molding method, however, if the primary molded piece is also a hollow element, there is a possibility that to fill the cavity with molten resin while closing the molding die completely allows the primary molded piece to be subjected to excessive injection pressure thereby causing the primary molded piece to be deflected or collapsed. Additionally, the arrangement of the primary molded piece on the concave bottom surface of the lower die may cause a problem of short shot since the underside of the primary molded piece is not supplied with molten resin.